Field of the Invention
The present invention relates to an exhaust muffler and a sound deadening element.
Description of Related Art
In the past, in an exhaust muffler of a vehicle, glass wool is inserted for thermal insulation and sound deadening.
In Japanese Patent Laid-Open No. 1999-324641, a technology is disclosed that, in order to prevent scattering of glass wool when glass wool is inserted as a sound deadening element into an exhaust muffler, a bundled element configured by bundling a great number of continuous fibers is overlaid and fixedly adhered in a planar shape to the glass wool. Also it is disclosed that such a planar bundled element as just described is folded back and disposed in an exhaust muffler.
A sound deadening element in an exhaust muffler is formed in a glass mat by a fabrication method such as, for example, needle punch using short glass fibers in order to apply the sound deadening element to a portion upon which exhaust gas having a high flow velocity and a high temperature directly hits. Therefore, intertwined fibers are likely to be scattered by the back pressure of the exhaust gas. On the other hand, a technique is available that a glass mat is impregnated with a binder having, for example, colloidal silica as a principal component and shaped to solidify the mat having flexibility to improve the anti-scattering property. In this case, the shaped sound deadening element cannot be assembled to a cylindrical portion, and therefore, it becomes necessary to add a slit or the like, and the glass wool is scattered from the slit. Accordingly, a sound deadening element that has a high anti-scattering property and does not require shaping is demanded.
On the other hand, in the exhaust muffler and the sound deadening element disclosed in Japanese Patent Laid-Open No. 1999-324641, a great number of fiber ends exist, which similarly degrades the anti-scattering property. Further, such a process for preventing exposition of fiber ends is demanded, which increases the number of processing steps.